A novel experimental method for rapid qualitative characterization of heterogeneous mixtures of macrosolutes has been proposed, based upon analysis of the time and concentration dependence of two experimentally measurable parameters called the apparent sedimentation and diffusion coefficients. A simple method for reducing the duration of a conventional sedimentation equilibrium by a factor of approximately five has been proposed. The interaction between fibrous rabbit muscle actin and several globular proteins has been investigated via size exclusion chromatography, sedimentation, and viscosity measurement. A PC-based data acquisition and control system for the UV-visible scanner on the Beckman Model E analytical centrifuge has been developed and installed. An approximate theory has been formulated for the dependence of the diffusion coefficient of each species of protein upon the concentrations of all species in a mixture of globular proteins.